A related-art refrigeration cycle apparatus includes: a low-stage refrigeration cycle that includes a low-stage compressor, a low-stage condenser, a low-stage pressure reducing device, and a low-stage evaporator, and circulates low-stage refrigerant; a high-stage refrigeration cycle that includes a high-stage compressor, a high-stage condenser, a high-stage pressure reducing device, and a high-stage evaporator, and circulates high-stage refrigerant, a cascade condenser exchanging heat between the low-stage refrigerant in the low-stage condenser and the high-stage refrigerant in the high-stage evaporator, and a controller. Such a refrigeration cycle apparatus uses CO2 refrigerant as the low-stage refrigerant (refer to Patent Literature 1).